WO 96/40156 and WO 96/40190, each published Dec. 19, 1996, disclose therapeutic derivatives of diphosphonates. These compounds have the formula A--V' and are obtained by reacting a diphosphonic acid compound with a pharmaceuticaly active entity. In these compounds of formula A--V', A is the residue of a pharmaceutically active entity and V' is the residue of the diphosphonic acid compound.